Fixes #72 - Restructured arb int math and enabled BCMath as an engine

And this time shouldn't stall Travis CI
Thanks for bringing this up.  Since writing it I think it might be better to put this in the nonce code itself.  It's a fix for the way we are currently generating nonces, and if we used a different method, it wouldn't need to be in the test. Having our nonce function usleep(1) and then return the microtime, and removing this from the test would be better design.